Sheet feeding apparatus of the general type herein disclosed has become widely used in the corrugated container industry and heavy manual labor has thus been eliminated at various points throughout the typical box plant. Such automatic feeding apparatus is utilized in the feeding of printer-slotters, die cutters, folder-gluers and the like. An apparatus of this type is disclosed in the Hoke et al., U.S. Pat. No. 3,815,762.
Where the press hopper or other apparatus is being fed by a feed transfer conveyor which presents the sheets sequentially, in "shingled" or overlapping form, to the apparatus, the reloading cycle of the sheet feeding apparatus presents difficulties. Since the feeder cradle must be loaded in stack-size increments, in the time interval between feeding of the last sheet from the cradle and the feeding of the initial sheets from the reloaded cradle (the time necessary for the cradle to move through its reloading cycle) a gap is created on the shingle or series flow of sheets on the feed transfer conveyor. The apparatus of the present invention overcomes this difficulty by moving the cradle horizontally, after each reloading of the craddle, toward the receiving conveyor an amount sufficient to cover the feeding gap caused by the excursion of the cradle through its load position. Elimination of this gap in the shingle or sequence feeding the press between cradle loadings makes unnecessary the intermittent stoppage of the press for feeder reloading, a characteristic of prior art feeding apparatus. The general subject of cradles is well known and is shown in, for example, U.S. Pat. Nos. 3,982,750, 2,707,568 and 2,863,571.
The capability for horizontal motion of the cradle is also utilized during momentary stoppages of the press or other apparatus being fed. If, during feeding or "shingling" of sheets from the cradle to the receiving conveyor the receiving conveyor should stop, because the press hopper is full, for example, the cradle will continue feeding sheets but will retreat horizontally away from the receiving conveyor. Since the dispensing tip of the cradle overlies the receiving conveyor, sheets will be deposited along the momentarily stationary, receiving conveyor. The feed sequence is thus unbroken upon momentary receiving conveyor stoppages. When the conveyor restarts, the cradle will halt its retreating, horizontal motion and continue feeding sheets to the now-moving receiving conveyor. If the receiving conveyor again halts, the cradle will continue its retreat until a predetermined home position is reached. When emptied, and in this home position, the cradle will immediately go through its reloading cycle and then advance forward on the receiving conveyor to its advanced position and begin feeding sheets from its newly loaded stack.
The apparatus of the present invention is further characterized by a generally L-shaped cradle which receives a stack load between shaped members forming its upright leg. Load support members are then moved to a position between the spaced leg members and support the tipped stack when the cradle is pivoted into feeding position. The pivotal axis of the cradle is at a level such that when the cradle has been moved to feed position and the included angle between the cradle legs has been increased from 90.degree. to approximately 180.degree., the sheets will be fed from the cradle substantially horizontally onto the receiving conveyor. The up-hill feed characteristic of conventional feed apparatus is thus eliminated.
The invention disclosed herein also includes an adjustable backstop assembly to control the thickness of flow of the shingled sheets moving on the conveyor. In U.S. Pat. No. 3,815,762, there is disclosed a vertical wall for allowing sheets to accumulate on a conveyor prior to passing between the wall and conveyor. Likewise in U.S. Pat. No. 3,905,487, a gate is provided to momentarily stop the flow of sheets on a conveyor.